Convert a device's public IP address to CIDR notation and update ingress rules on Oracle Cloud Infrastructure Network List to allow ingress from current device to devices configured on our VCN

open-sesame.sh

#!/bin/bash
# Deepraj Pandey
# 06 August 2024
# 
# Convert a device's public IP address to CIDR notation and update ingress rules on Oracle Cloud Infrastructure
# Network List to allow ingress from current device to devices configured on our VCN
# 
# Dependencies: OCI cli tool installed and configured with a ~/.oci/config file

# Enable alias expansion and load custom aliases (oci setup)
shopt -s expand_aliases
source ~/.shell_local_after

public_ip_in_cidr() {
    local ip
    local public_ip
    local octet
    local binary_octet
    local leading_zeros
    local cidr_prefix

    ip=$(dig -4 TXT +short o-o.myaddr.l.google.com @ns1.google.com)

    # Remove the double quotes from the IP address
    public_ip=$(echo "$ip" | tr -d '"')
    # echo "[DEBUG] Preprocessed IP Address: ${public_ip}"

    # local public_ip=$(dig +short myip.opendns.com @resolver1.opendns.com)
    # echo "[DEBUG] Public IP Address: ${public_ip}"

    octet=$(echo "$public_ip" | awk -F '.' '{print $4}')
    # echo "[DEBUG] octet=${octet}"

    binary_octet=$(printf "%08d" $(echo "obase=2; ${octet}" | bc))
    # echo "[DEBUG] binary octet=${binary_octet}"

    leading_zeros=$(echo "${binary_octet}" | grep -o "^0*" | wc -c)
    leading_zeros=$((leading_zeros - 1))  # Correct for extra space
    # echo "[DEBUG] leading zeros=${leading_zeros}"

    cidr_prefix=$((32 - (8 - leading_zeros)))

    # Ensure the CIDR prefix >= 24
    if [ "$cidr_prefix" -lt 24 ]; then
        cidr_prefix=24
    fi
    # echo "[DEBUG] CIDR prefix=${cidr_prefix}"

    # echo "[DEBUG] IP Address in CIDR notation"
    echo "${public_ip%.*}.0/${cidr_prefix}"
}

# Get the public IP in CIDR notation
source_ip=$(public_ip_in_cidr)

# Update source in ingress rules json
sed -i -e '32s|"source": "[^"]*"|"source": "'"${source_ip}"'"|' ~/.oci/ingress-security-rules.json

# Parse the -d flag for debug mode
debug_mode=false
while getopts "d" opt; do
    case $opt in
        d)
            debug_mode=true
            ;;
        \?)
            echo "Invalid option: -$OPTARG" >&2
            exit 1
            ;;
    esac
done

# Run the OCI command with or without debug mode
if $debug_mode; then
    oci network security-list update --security-list-id ocid1.securitylist.oc1.ap-mumbai-1.aaaaaaaa6zsni7mcr75ixcvhdadgbwspi3dl7njrdfudi3sijlxunt54pkya --ingress-security-rules "file://~/.oci/ingress-security-rules.json" --debug
  else
    oci network security-list update --security-list-id ocid1.securitylist.oc1.ap-mumbai-1.aaaaaaaa6zsni7mcr75ixcvhdadgbwspi3dl7njrdfudi3sijlxunt54pkya --ingress-security-rules "file://~/.oci/ingress-security-rules.json"
fi